Machine for setting rivets



June 28, 1966 D. G. DOWNES MACHINE FOR SETTING RIVETS Filed Aug. 15, 1963 R m V m United States Patent 3,257,837 MACHINE FOR SETTING RIVETS Douglas G. Downes, Sawyer Road, Natick, Mass. Filed Aug. 15, 1963, Ser. No. 302,335 7 Claims. (Cl. 72437) This invention relates to machines for setting rivets and more particularly comprises a new and improved top lever assembly for rivet setting machines.

In one widely used form of rivet setting machines a rocker assembly is employed, which includes a centrally pivoted top lever connected at one end to the drive mechanism and at its other to the plunger which sets the rivets. Conventionally this form of rivet setting machine includes a short generally vertical link pivotally supported at its lower end on the frame and in turn pivotally supporting the top lever. Because the stroke of the plunger carried at one end of the top lever is confined to a fixed path, the link is essential to allow the top lever to shift laterally as it rocks on its pivotal support. Without the pivotal link the plunger axis would shift back and forth as the top lever rocked, and the plunger would not apply the clinching force to the rivet being set along the rivet axis. As a result, the rivet would tip and/ or one part of its periphery would be clinched tighter than the other, which in turn would likely mar the work into which the rivet is mounted.

The pivotally supported generally vertical links used in rivet setting machines of the type described very often deviate as much as fifteen degrees or more from the vertical position during each cycle of the top lever and this pivotal movement of the link introduces side thrusts in the frame of a very considerable magnitude. These substantial side loads applied to the frame necessitate the use of a very massive and consequently expensive casting to absorb such extraneously applied loads. T he side loads also tend to cause misalignment of the plunger and the anvil of the machine. have a tendency to bell mouth the plunger guide, which may cause the plunger to chatter as it moves up and down with the rocking top lever.

The short generally vertical links used to support the top levers, so far as is known, have universally been mounted near or at the top of the machine frame and appreciably forward of the central vertical column of the frame toward the plunger guide bracket. As a result, the links apply forceson the frame which tend to open the forward portion of the frame and disturb the alignment of the plunger and the anvil, which causes improper clinching of the rivets.

In all known rivet setting machines the energy applied to the operating mechanism during the return stroke of the plunger far exceeds the energy required. However, as

the power drive for the operating mechanism is ordinarily a motor driven crank shaft no way has been devised for cyclicly reducing the power output of the motor without seriously impairing the usefulness of the machine. As

a result, the clutch and brake mechanism of rivet setting machines have been required to absorb the substantial excessive forces during a portion of each cycle of the machine, and only very heavy duty clutch and brake mechanisms are capable of performing this function.

One important object of this invention is to provide a rivet setting machine having a top lever assembly which does not apply forces upon the frame of the machine tend to cause misalignment.

Another important object of this invention is to greatly reduce the size, Weight and cost of the frames of a rivet setting machine without reducing the machine capacity.

Still another important object of this invention is to increase the efiiciency of rivet setting machines.

A more specific object of this invention is to store for Moreover, the side loads.

3,257,837 Patented June 28, 1966 "ice later utilization power previously dissipated and wasted during the return stroke of the operating mechanism.

To accomplish these and other objects, my invention includes among its features a generally vertical elongated link for supporting the top lever of the operating mechanism. The elongated link is pivotally mounted on the frame preferably below the lower end of the plunger stem at the approximate level of the anvil arm, and the link restricted to pivotal movement about its lower support, of but a few degrees. The length of the link is appreciably greater than the links now employed and consequently afford the same lateral displacement to the top lever pivotal axis without introducing side thrusts on the machine of an appreciable magnitude. Because the reaction forces are imparted to the frame at the approximate height of the anvil, the massive frame previously required to resist the reaction forces tending to open the frame may be eliminated.

As yet another feature, this invention includes an accumulator which stores energy during the return stroke of the operating mechanism and then releases the energy during the forward stroke of the next cycle to assist the motor or other prime mover employed.

These and other objects and features of this invention, along with its incident advantages, will be better understood and appreciated from the following detailed description of one embodiment thereof, selected for purposes of illustration and shown in the accompanying drawing, in which:

FIG. 1 is a fragmentary side view of a rivet setting machine embodying the invention; and

FIG. 2 is a fragmentary top view of a part of the assembly 'shown in FIG. 1.

In the drawing many of the parts ofv the rivet setting machine have been omitted such as the machine housing, clutch mechanism, operating controls and rivet hopper because they form no part of the present invention. However, the drawing does illustrate a machine having a base 10, a frame 12, a plunger assembly 14, a driving mechanism 16, a top lever assembly 18 and an accumulator 20. In use, the base 10 may be mounted on a pedestal, table or other support to hold the machine at a height convenient for an operator. In FIG. 1 the accumulator 20 is shown in its loaded position assumed when the top lever assembly 18 is pivoted through arc ,6.

The frame 12 secured to the base 10 is in the form of an angle casting having a vertical front plate22 and a horizontal base plate 24 with the latter conveniently bolted to the base 10. The vertical front plate 22 carries a forwardly extending arm 26 secured in place by several cap screws 28. The-arm 26 carries an anvil 30 having an upstanding retractible pilot 32, which may take any conventional form. The anvil 30 serves as the base against which rivets set by the machine are crimped during the machines operation.

The vertical front plate 22 of the frame 12 also carries a right angle bracket support 34 secured in place by cap screws 36 (one shown) and which in turn supports the plunger bracket 38. The plunger bracket 38 maybe secured in place on the horizontal arm of the support by screws or other appropriate fasteners. A vertically oriented guideway 40 alinged axially with the anvil 30 is formed in the plunger bracket 38 to guide movement of the plunger 42 during the rivet setting operation. Preferably the guideway 40 and the plunger 42 are circular in cross section as the round configuration is less costly to fabricate andis the optimum shape. Nevertheless each may take other cross-sectional forms such as a square, rectangle, etc. The plunger 42 carries a stem 44 which actually engages the rivet as it is set by the machine. The plunger stem 44 drives the rivet from the pocket 46 in a which the rivet has previously been deposited by the rivet hopper (not shown).

The plunger 42 is reciprocally moved in the guideway 40 by the top lever assembly 18. This assembly embodies many of the salient features of the present invention. The assembly includes a top lever 50 supported adjacent its center for pivotal movement on the upper end of the vertical link 52. A pivot pin 54 extends through an opening formed in the top lever 50 and a similar opening in the upper end 56 of the vertical link 52 to define a fulcrum for the top lever.

Both the forward end 58 and the rear end 60 of the top lever 50 are bifurcated. Thus, two cars 62 on the front end 58 of the lever lie on opposite sides of the upper end 64 of the plunger 42. Bushing 66 and connecting pin 68 join the ears 62 to the upper end 64 of the plunger 42 so that rocking of the top lever 50 about its fulcrum will cause reciprocal movement of the plunger. Similarly, cars 70 of the rear end 60 of the top lever are disposed on opposite sides of the upper end 72 of a connecting rod 74, and the two are secured together by bushing and pin 76 and 78, respectively. The connecting rod 74 is connected to the crank shaft 80 which in turn is connected through a clutch (not shown) .to a fly Wheel 82. The crank shaft 80 along with the fly wheel 82 may be supported on a pair of spaced posts 84 (one shown) bolted to the base 10. The .fiy wheel 82 is driven by a belt 86 and pulley 88 in turn driven by the shaft of motor 90. The motor 90 as viewed in FIG. 1 is also supported on the base 10.

Because motion of the plunger 42 is confined to an axial direction in the guideway 40 of the bracket 38, the axis of the pin 68 must remain normal to and intersect the guideway axis throughout the movement of the top lever 50. Thus, when the pin axis moves from position 68a to 68b, the fulcrum of the top lever 50 must shift. This is accomplished by supporting the vertical link 52 on a pivot pin 92 extending through the web 94 of the frame 12. By mounting the link 52 on the pin 92 the pivot point or axis of the top lever as defined by the axis of the pin 54 may shift to the point 54b so that the axis of pin 68 remains in a plane containing the guideway axis. Thus, the link 52 swings through angle on when the top lever 50 moves through angle ,8 from the position shown in full lines to that suggested by the broken center line 50b in FIG. 1.

As suggested, the top lever 50 is made to move from the position suggested by line 50a to that suggested by line 50b when the crank shaft 80 turns through 180. During that portion of the cycle the crank arm 96 moves from the position shown in full lines in the drawing to its lowest position suggested by dotted line 9612. Continued rotation of the crank 80 of course returns the crank arm to the position shown in full lines. Thus, during each revolution of the crank shaft the crank arm moves from the position 96b and through the three positions 96a, 96 and 96c and returns to the lowest position 9617.

It is apparent that the forces applied to the top lever 50 through the connecting rod 74 and the forces applied to the other and of the top lever '50 through the plunger 42 by the rivet being crimped must be balanced by a force applied to the top lever through the vertical link 52. -If the link 52 deviates an appreciable angle from the vertical (angle a become large) the force applied by the link 52 on the top lever 50 has a substantial horizontal component which must be borne by the guideway 40. In such cases the plunger bears heavily against the side of the guideway and will wear that side and bell-mouth the ends of the guideway 40. This allows the plunger axis 42 to shift angularly and become misaligned with the anvil axis.

To eliminate the substantial side thrust exerted by the vertical link on the top lever 50 and through that lever upon the other parts of the equipment, the link 52 is made considerably longer than links presently used on rivet setting machines. In this manner the angle at required to achieve displacement of the axis of the pin 54 from position 54:: to 541) is markedly reduced, and the side thrust is correspondingly reduced as it varies with the tangent of the angle. It .will be appreciated that if the length of the link 52 is increased by a factor of two, the angle a required to achieve the particular displacement of the axis of the pin 54 is halved, and the tangent is correspondingly reduced when the angle is small. Because the side thrust is reduced to a minimum the entire mass of the frame required to oppose the side thrust is also greatly reduced, and the machine is lightened and made much less costly. With small angles. the tangent is substan- .tially proportional to the angle and therefore the reduction in the angle of displacement 0: produces a proportional reduction in side thrust upon the machine.

In the drawing it will be noted that the unusually long vertical link 52 is tied to the frame appreciably below the plunger bracket 38 and the point at which that bracket is supported on the frame. In the drawing the pin 92 is shown to be disposed at the height of the arm 26 supporting the anvil 30. It has been universally the practice to support the shorter links now used above the midpoint of the plunger bracket, and ordinarily a connection was made to the frame above the bracket and the space 100 between the bracket and the arm 26. As a result, any forces applied by the link to the top lever 50 produced a corresponding reaction force on the frame which tended to bend the plunger bracket upwardly away from the arm 26. That is, the reaction force would tend to pivot or swing the bracket 38 upwardly and rearwardly and cause misalignment of the plunger axis and the axis of the anvil. In order to counteract the tremendous forces applied to the machine frame which would otherwise misalign those axes, the frame of the prior art machines took the form of a very large casting which were both heavy and costly. Thus, the small links currently employed to support the top levers not only create substantial side thrust which necessitate frames of large size .to counteract them, but in addition, apply vertical forces upon the frames which cause the frames to open. A longer link reduces the side thrust and also applies a vertical component of the reaction force below the point where it can have a tendency to open the frame and cause misalignment of the anvil and plunger axes.

Further advantages may be achieved if the vertical link 52 is made of nylon or some other material having comparable strength and resiliency and which acts in compression in the same manner as nylon. Nylon is characterized as being substantially noncompressible up to some critical value and is resiliently compressible under pressures which exceed that value up to a fatigue value. If the post 51 is made of nylon it will remain substantially non-compressible and of uniform length under ordinary operation of the machine, but should the plunger and more particularly its stem encounter some unusual resisting force during its upward travel, some of the stress applied to the plunger could be relieved when the corresponding load on the vertical link 52 exceeds the critical value. When this occurs the link 52 could compress somewhat and reduce the travel of the plunger required to permit the crank 96 to complete its cycle.

In virtually all known rivet setting machines productive work is performed only during one half of the cycle "of the top lever-that is, only when the top lever rocks in a counterclockwise direct-ion as viewed in FIG. 1 to drive the plunger from a raised position to a lowermost position where it engages and clinches the rivet. During the other half of the cycle when the lever is moved clockwise about its fulcrum the power was completely wasted except for the little energy required to physically elevate the plunger and pivot the top lever. This energy which previously has been dissipated by the brake so as to relieve part of the stress upon the clutch is accumulated in the present invention by the accumulator 20. The accumulator includes a cylinder 110 pivotally supported at its bottom on the frame by pin 112. The pin 112 allows the cylinder 110 to pivot about a horizontal axis as suggested in FIG. 1 by broken line 110a. The cylinder 110 is open at the top and a piston 114 carried on piston rod 116 may move up and down in the cylinder 110. The piston 114 defines with the walls of the cylinder 110 a closed chamber 118 which houses a spring 120 that acts in compression to elevate the piston 114 in the cylinder. The piston rod 116 carries an adjusting nut 122 at its lower end which bears against the upper surface -of the piston 114 and moves the piston downwardly into the cylinder 110 as the piston rod 116 is driven downwardly under the influence of the top lever 50. The upper end 124 of the rod carries a C-shaped coupling 126 tied to the top lever by pin 128. Thus, as the rear portion of top lever 50 rocks up and down on its fulcrum established by the pin 54, the piston rod 116 moves up and down and carries the piston 114 with it. When the rod moves down and lowers the piston 114 it compresses the spring 120 which thereby stores energy which is released as the spring expands. Thus, during the return stroke of the plunger 42 when it is elevated in the bracket 38 and the connecting rod 74 secured to the crankshaft 80 moves downwardly as the crank arm 96 moves from the position shown in full lines to that-shown in 96b, the energy otherwise wasted and dissipated by the brake is utilized to compress the spring 120 in the accumulator which in turn releases energy during the forward or down stroke of the plunger. In essence, when the crank moves from the position shown in 96b in broken lines to the position shown in full lines (180) the spring expands and assists the crank arm. During the following 90 the top lever motion is accelerated and during the last 90 of the cycle when the crank arm returns to the position shown in 96b, the spring is compressed and energy is stored for the next cycle. The spring not only serves to store energy and release it for the next cycle, but serves as a damper to absorb the shock which otherwise would be encountered and applied to the brake.

From the foregoing description many of the advantages of this invention become apparent. The elimination of stress upon the machine frame which causes distortion and wear of the machine, and misalignment of the parts is eliminated. Consequently a much smaller frame casting may be employed which results in making room available for control boxes, circuitry and other ancillary equipment within the confines of the housing (not shown) which surrounds the assembly. Ordinarily a housing is provided of rather streamline shape which encases the parts shown in FIG. 1 with the exception of the forward portion of the plunger bracket, the plunger, the arm 26 and the anvil. The sides of the housing ordinarily lie rather close to the sides of the top lever, link and fly wheel and heretofore the frame which was relatively massive occupied virtually the remaining parts of the housing chamber. By virtue of the room saved by the elimination of the frame a substantial space is now available within the housing and between such parts as the vertical link and the accumulator or between the accumulator and'connecting rod and the drive, which can house the auxiliary equipment formerly mounted on the outside of the housing.

Experimentation indicates that the weight of the machine may be reduced from in excess of 800 lbs. to ap proximately 100 lbs. because of the elimination of the massive frame formerly required to absorb or counteract extraneous forces. The longer link and the smaller angle through which it moves enables the machine to employ an appreciably longer stroke. The increased stroke greatly increases the output of the machine. Thus, the size of the motor may be reduced without sacrificing output. The efficiency of the machine is approximately 62% as opposed to 16% for conventional equipment of the prior art.

Because numerous modifications may be made of this invention without departing from its spirit, it is not intended that the birth of this invention be determined by the single embodiment illustrated and described. Rather, it is intended that the breadth of this invention be determined by the appended claims and their equivalents.

What is claimed is:

l. A rivet setting machine comprising a base,

a frame mounted on the base and carrying a forwardly extending arm, said arm supporting rivet engaging means,

a plunger bracket mounted on and extending forwardly and upwardly from the frame and aligned above the arm, i

a generally vertical link mounted at its bottom on the frame at the approximate height of the arm and rearwardly of the bracket and the arm,

and a top lever mounted intermediate its ends on the top of the link and extending forwardly over the top of the bracket and aligned with the bracket and arm a plunger supported by said bracket for vertical movement to an away from said arm with one end of said plunger secured to said top lever and the other end carrying rivet engaging means, and means for upward and downward reciprocation of said top lever whereby said plunger is moved toward and away from said arm.

2. A rivet setting machine comprising abase,

a frame mounted on the base and carrying a forwardly extending arm, said arm supporting rivet engaging means,

a plunger bracket mounted on and extending forwardly and upwardly from the frame and aligned above the arm,

' a generally vertical link mounted at its bottom on the frame rearwardly of the bracket and the arm,

and a top lever mounted intermediate its ends on the top of the'link and extending forwardly over the top of the bracket and aligned with the bracket and arm a plunger supported by said bracket for vertical movement to an away from said arm with one end of said plunger secured to said top lever and the other end carrying rivet engaging means, and means for upward and downward reciprocation of said top lever whereby said plunger is moved toward and away from said arm.

3. A rivet setting machine as defined in claim 2 further characterized by said link being made of nylon.

4. A rivet setting machine comprising a base,

a frame mounted-on the base and carrying a forwardly extending arm, said arm supporting rivet engaging means,

a plunger bracket mounted on and extending forwardly and upwardly from the frame and aligned above the arm,

a generally vertical link mounted adjacent its bottom on the frame below the point of connection between the bracket and the frame,

and a top lever mounted intermediate its ends on the top of the link and extending forwardly over the top of the bracket and aligned with the bracketand arm, a plunger supported by said bracket for vertical movement to an away from said arm with one end of said plunger secured to said top lever and the other end carrying rivet engaging means, and means for upward and downward reciprocation of said top lever whereby said plunger is moved toward and away from said arm.

5. A rivet setting-machine as defined in claim 4 further characterized by an accumulator connected between the top lever and the frame and acting in compression to assist the downward travel of the forward end of the top lever. 6. In a rivet setting machine, a frame and an arm extending outwardly from the frame, an anvil extending upwardly from the arm, a link pivotally mounted on the frame at the approximate height of the arm, a top lever pivotally secured at its center to the top of the link and extending horizontally over the center of the anvil, a plunger pivotally secured to the end of the top lever over the anvil, a bracket secured to the frame and supporting the plunger for upward and downward movement in a vertical direction toward and away from the anvi], and an energy source secured to the other end of the top lever for pivoting it on the top of the link and driving the plunger up and down in its bracket, said energy source including a motor driven crankshaft connected to said other end of the top lever which shaft in a single revolution drives the plunger through a full cycle, an accumulator secured to the frame and including a member which acts in compression to store energy, said member being secured to the top lever and being compressed during the return stroke of the lever under the influence of the crankshaft, said accumulator acting with the crankshaft for driving the lever during the forward stroke of the cycle.

7. In a rivet setting machine having a top lever supported for pivotal movement about a horizontal axis and having a plunger secured at one end and a driving member connected to the other, an accumulator secured to the lever and storing energy during the return stroke of the lever and discharging the energy into the motion of the lever during the drive stroke of the lever, said accumulator comprising a sleeve, a spring disposed in the sleeve, a rod secured to the lever and carrying a piston disposed in the sleeve and acting upon the spring to compress it during the return stroke of the driving member.

References'Cited by the Examiner UNITED STATES PATENTS 862,391 8/1907 Hamlett 72437 1,562,988 11/1925 Nelson 72437 2,475,398 7/1949 Montoya 72-437 3,043,168 7/1962 May 7848 FOREIGN PATENTS 123,895 1901 Germany. 564,726 10/1944 Great Britain.

CHARLES W. LANHAM, Primary Examiner.

G. P. CROSBY, Examiner. 

1. A RIVET SETTING MACHINE COMPRISING A BASE, A FRAME MOUNTED ON THE BASE AND CARRYING A FORWARDLY EXTENDING ARM, SAID ARM SUPPORTING RIVET ENGAGING MEANS, A PLUNGER BRACKET MOUNTED ON SAID EXTENDING FORWARDLY AND UPWARDLY FROM THE FRAME AND ALIGNED ABOVE THE ARM, A GENERALLY VERTICAL LINK MOUNTED AT ITS BOTTOM ON THE FRAME AT THE APPROXIMATE HEIGHT OF THE ARM AND REARWARDLY OF THE BRACKET AND THE ARM, AND A TOP LEVER MOUNTED INTERMEDIATE ITS ENDS ON THE TOP OF THE LINK AND EXTENDING FORWARDLY OVER THE TOP OF THE BRACKET AND ALIGNED WITH THE BRACKET AND ARM A PLUNGER SUPPORTED BY SAID BRACKET FOR VERTICAL MOVEMENT TO AN AWAY FROM SAID ARM WITH ONE END OF SAID PLUNGER SECURED TO SAID TOP LEVER AND THE OTHER END CARRYING RIVET ENGAGING MEANS, AND MEANS FOR UPWARD AND DOWNWARD RECIPROCATION OF SAID TOP LEVER WHEREBY SAID PLUNGER IS MOVED TOWARD AND AWAY FROM SAID ARM. 